Trains.pdf

Meteors, especially fireballs, can leave behind a glowing trail known as a train, which can persist for several seconds. The physics behind this phenomenon is not fully understood. There are two types of trains: regular trains that emit light and smoke trains that do not. Regular trains are formed when a meteoroid enters the Earth's atmosphere and its surface atoms sublimate and turn into ions, while smoke trains are composed of dust particles. Both types of trains can be observed at altitudes above 20 km, where strong winds can cause them to distort.

To photograph regular trains, a camera with high sensitivity film and a fast lens should be used, with the shutter already open and covered. When a bright meteor appears, the cover is removed and the film is exposed for 20-40 seconds. For smoke trains, which are visible during daylight or twilight, normal daylight photography rules apply, and a series of exposures should be taken to record the train's shape and brightness.

The equipment required to photograph trains includes a camera with a fast lens and film, and the ability to take multiple exposures. The timing and duration of the exposures depend on the brightness of the train and the sky. Observing smoke trains during twilight can provide information about the upper atmosphere and the material brought into the atmosphere by the meteoroid.